sapply improvements

On 11/4/2009 12:15 PM, William Dunlap wrote:

-----Original Message-----
From: r-devel-bounces at r-project.org
[mailto:r-devel-bounces at r-project.org] On Behalf Of Duncan Murdoch
Sent: Wednesday, November 04, 2009 8:47 AM
To: michael.m.spiegel at gmail.com
Cc: R-bugs at r-project.org; r-devel at stat.math.ethz.ch
Subject: Re: [Rd] error in install.packages() (PR#14042)

On 11/4/2009 11:05 AM, michael.m.spiegel at gmail.com wrote:

Full_Name: Michael Spiegel
Version: 2.10
OS: Windows Vista
Submission from: (NULL) (76.104.24.156)

The following error is produced when attempting to call
install.packages. ?Here

is the results of the traceback:

source('http://openmx.psyc.virginia.edu/getOpenMx.R')

Error in f(res) : invalid subscript type 'list'

traceback()

7: f(res)
6: available.packages(contriburl = contriburl, method = method)
5: .install.winbinary(pkgs = pkgs, lib = lib, contriburl = contriburl,

? ? ? ?method = method, available = available, destdir = destdir, >

?dependencies = dependencies, ...)
4: install.packages(pkgs = c("OpenMx"), repos = repos)
3: eval.with.vis(expr, envir, enclos)
2: eval.with.vis(ei, envir)
1: source("http://openmx.psyc.virginia.edu/getOpenMx.R")

I've tracked the error down to somewhere in available.packages
defined in

src\library\utils\R\packages.R. ?I am guessing that the error in
version 2.10
has something to do with the change: "available.packages() gains a
'filters'
argument for specifying the filtering operations performed on the
packages found
in the repositories."

I've found the error, and will fix and commit to R-devel and R-patched.

For future reference: ?the problem was that it assigned the result of
sapply() to a subset of a vector. ?Normally sapply() simplifies its result
to a vector, but in this case the result was empty, so sapply() returned an
empty list; assigning a list to a vector coerced the vector to a list, and
then the "invalid subscript type 'list'" came soon after.

I've run into this sort of problem a lot (0-long input to sapply
causes it to return list()). ?A related problem is that when sapply's
FUN doesn't always return the type of value you expect for some
corner case then sapply won't do the expected simplication. ?If
sapply had an argument that gave the expected form of FUN's output
then sapply could (a) die if some call to FUN didn't return something
of that form and (b) return a 0-long object of the correct form
if sapply's X has length zero so FUN is never called. ?E.g.,
? sapply(2:0, function(i)(11:20)[i], FUN.VALUE=integer(1)) # die on
third iteration
? sapply(integer(0), function(i)i>0, FUN.VALUE=logical(1)) # return
logical(0)

Another benefit of sapply knowing the type of FUN's return value is
that it wouldn't have to waste space creating a list of FUN's return
values but could stuff them directly into the final output structure.
A list of n scalar doubles is 4.5 times bigger than double(n) and the
factor is 9.0 for integers and logicals.

What do you think of the behaviour of the sapply function below? ?(I
wouldn't put it into R as it is, I'd translate it to C code to avoid the
lapply call; but I'd like to get the behaviour right before doing that.)

This one checks that the length() and typeof() results are consistent. If
the FUN.VALUE has names, those are used (but it doesn't require the names
from FUN to match).

Duncan Murdoch

sapply <- function(X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE,
FUN.VALUE)
{
? ?FUN <- match.fun(FUN)
? ?answer <- lapply(X, FUN, ...)
? ?if(USE.NAMES && is.character(X) && is.null(names(answer)))
? ? ? ? ? ? ? ?names(answer) <- X
? ?if(simplify) {
? ? ? ?if (missing(FUN.VALUE)) {
? ? ? ? ? ?if ((!length(answer))
? ? ? ? ? ? ? ?|| length(common.len <- unique(unlist(lapply(answer,
length)))) != 1L)
? ? ? ? ? ? ? ?return(answer)
? ? ? ? ? ?common.names <- names(answer[[1L]])
? ? ? ?} else {
? ? ? ? ? ?common.len <- length(FUN.VALUE)
? ? ? ? ? ?common.type <- typeof(FUN.VALUE)
? ? ? ? ? ?common.names <- names(FUN.VALUE)
? ? ? ? ? ?if (length(answer)) {
? ? ? ? ? ? ? ?if (any( unlist(lapply(answer, length)) != common.len ))
? ? ? ? ? ? ? ? ? ?stop(sprintf("%s values must be of length %d", "FUN",
common.len))
? ? ? ? ? ? ? ?if (any( unlist(lapply(answer, typeof)) != common.type ))
? ? ? ? ? ? ? ? ? ?stop(sprintf("%s values must be of type '%s'", "FUN",
common.type))
? ? ? ? ? ? ? ?if (is.null(common.names))
? ? ? ? ? ? ? ? ? ?common.names <- names(answer[[1L]])
? ? ? ? ? ?} else if (length(FUN.VALUE) > 1)
? ? ? ? ? ? ? ?return(array(FUN.VALUE[0], dim=c(common.len, 0),
? ? ? ? ? ? ? ? ? ? ? ? ? ? dimnames= if(!is.null(common.names))
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? list(common.names,character(0))))
? ? ? ? ? ?else
? ? ? ? ? ? ? ?return(FUN.VALUE[0])
? ? ? ?}
? ? ? ?if(common.len == 1L)
? ? ? ? ? ?unlist(answer, recursive = FALSE)
? ? ? ?else if(common.len > 1L)
? ? ? ? ? ?array(unlist(answer, recursive = FALSE),
? ? ? ? ? ? ? ? ?dim= c(common.len, length(X)),
? ? ? ? ? ? ? ? ?dimnames= if(!(is.null(common.names) &
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? is.null(n2 <- names(answer))))
list(common.names,n2))
? ? ? ?else answer
? ?} else answer
}